A Calculation Method of Absolute Phase of Multi-frequency Heterodyne Grating Based on Image Gray-scale Interval Expansion
A technology of interval expansion and image grayscale, which is applied in measurement optics, optical radiation measurement, instruments, etc., can solve the problems of increasing time for taking images and decreasing speed of three-dimensional measurement of structured light, so as to increase calculation speed, improve measurement accuracy and Effects of Efficiency, Reliability and Accuracy Guarantee
Active Publication Date: 2020-12-25
HEILONGJIANG UNIVERSITY OF SCIENCE AND TECHNOLOGY
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In addition to taking phase-shifted images, this method also needs to take a large number of other frequency phase-shifted images. The cost is that the time for taking images is significantly increased, and the possibility of interference is greater, and the speed of structured light 3D measurement is obvious. decline
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[0048] A calculation method for calculating the absolute phase of a multi-frequency heterodyne grating with extended image grayscale intervals generally consists of calculation processes such as grating design, image acquisition, image background separation, wrapping phase calculation, phase synthesis, phase continuity processing, and absolute phase calculation. It is characterized in that the scheme is realized by the following steps:
[0049] Step 1. According to the heterodyne principle, the fringe frequencies of the given three cosine grating images are respectively f 1 , f 2 , f 3 , f 1 , f 2 , f 3 Should meet the requirements of two levels of heterodyning;
[0050] f1 -2f 2 + f 3 = 1 (1)
[0051] Step 2. Set the resolution of the measuring equipment as m×n, then generate two groups of fringe frequencies according to the resolution of m×n as f 1 , f 2 , f 3 A two-dimensional array Ln of the grayscale values of the cosine raster image i , Lp i , where i={1,2...
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An image grayscale interval-extended multi-frequency heterodyne grating absolute phase calculation method solves the problem of calculating an absolute phase through a small number of images by meansof a grayscale extension method and a discrete signal filtering method. The adopted method comprises the steps that firstly, alternating components are separated from cosine grating images, and the gray scale intervals of the images are extended to increase the pixel distinction degree; wrapped phases of the images are calculated by means of Hilbert filtering of discrete signals instead of multistep phase shifting; and then a synthetic phase diagram of new frequencies is obtained through frequency mixing achieved according to a heterodyne method, and according to corresponding range intervalsof anti-trigonometric functions, synthetic phases are shifted to be continuous in a single cycle to meet the requirement of phase unwrapping. Calculation of the large-scale absolute phase is achievedthrough multi-stage phase heterodyning. The method has the advantages that the measurement efficiency is significantly improved, and the overall precision of the algorithm is improved; and compared with a phase shifting method, both the reliability and the precision are guaranteed, and the advantages of being simple and easy to operate are achieved.
Description
[0001] Technical field: [0002] The invention belongs to the field of three-dimensional measurement of structured light. The absolute phase is recovered by shooting two cosine grating images of three frequencies. The method does not require phase shift and has the advantages of less required images and strong anti-interference ability, which can greatly improve the measurement precision and efficiency. Background technique [0003] Absolute phase is the basis of stereo matching in structured light 3D measurement technology, which ensures the uniqueness of matching results, and the accuracy of absolute phase directly determines the accuracy of stereo reconstruction. The process of obtaining the absolute phase by periodically encoding the wrapped phase is phase unwrapping. The phase shift plus encoding technology is the earliest technology used in the calculation of phase unwrapping. The phase shift is used to obtain the wrapped phase, and the binary coded image is used to enco...
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IPC IPC(8): G01J9/00
CPCG01J9/00
Inventor 孟祥林何万涛赵灿郭延艳李景贺
Owner HEILONGJIANG UNIVERSITY OF SCIENCE AND TECHNOLOGY